How to Connect to ODBC via script or HTML

I want to access a MySQL database that I've set up as a standard ODBC datasource either using html, or straight vbscript using a free program like PHP.

I've got a web page that loads using PHP to populate a dropdown menu. When the user selects from the menu, I would like to populate another field based on what the user chose by going into my database.

The problem with PHP is that once the page is loaded, PHP is done. I want to be able change this value WITHOUT having to refresh the whole page.

I know this can be done thru Java or VB, but learning Java is hard, and VB is not free. Can vbscript do this...?

Is there a free program or service that can do what I'm asking?